Remove the rust-action based cache

[AdamGS]

Experimenting showed that just using sccache is generally better or roughly equal, at least for our current setup with runs-on backed storage.

[codspeed-hq]

Merging this PR will not alter performance

✅ 1254 untouched benchmarks
⏩ 1254 skipped benchmarks¹

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_{Comparing adamg/experiment-no-rust-cache (333fd6a) with develop (59918a4)}

Footnotes

1. 1254 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩